I see this error almost every time I open the comments on a post.
My server is lemm.ee. Does it not support the “mark as read” feature?
Good advice.
@CreatureSurvive@lemmy.world, this appears to be a change in the API for marking a post as read. See the reply in my cross-post.
As a workaround I turned off the “Mark Read” settings in Settings → Content Settings.